Power fluid

ABSTRACT

A working fluid for use in a Rankine cycle engine consists of a mixture of hexafluorobenzene and perfluorotoluene.

United States Patent Cassidy et al.

POWER FLUID Inventors: Frank H. Cassidy, Orangevale;

Ramon Garcia, Sacramento, both 7 of Calif.

[73 I Assignee: Aerojet-(ieneral Corporation,

El Monte. Calif.

Filed: Nov. 1, 1971 Appl. No.: 194,271

[52] US. Cl. 60/36, 252/67 [51] Int. Cl. F0lk 25/00 [58] Fieldof Search 60/36; 252/67, 78,

[56] References Cited UNITED STATES PATENTS 3,584,457 6/l97l Davoud 60/36 [451 Aug. 21, 1973 3,173,872 3/l965 Broadley 252/78 X 3,234,734 2/1966 Buss et al 60/36 FOREIGN PATENTS OR APPLICATIONS 294,243 6/1929 Great Britain 60/36 Primary Examiner-Martin P. Schwadron Asxistant ExaminerAllen M. Ostrager Attorney-Edward O. Ansell et al.

[5 7] 7 ABSTRACT A working fluid for use in a Rankine cycle engine consists of a mixture of hexafluorobenzene and perfluorotoluene.

7 Claims, 2 Drawing Figures PRIOR ART PAIEMEB MIFZI I973 d ki 26 V PRIOR ART Flq-l 1 I a I awe,'?r::,%:::s2:2""

Ami

Weight percent Hexufluorobenzene Fig.2

POWER FLUID BACKGROUND OF THE INVENTION supplied by such power sources as coal, oil, natural gases, and in more recent times, nuclear power systerns.

One way of obtaining this power supply has been in the use of the Rankine cycle engine, which employs an external heat source to vaporize a working fluid.

2. Description of the Prior Art There have been manyapplications of various working fluids utilizing the Rankine cycle for producing power generation. These include the patents to Davoud, U.S. Pat. Nos. 3,584,457; Tabor et al., No. 3,040,528; Murphy et al., No. 3,282,048; Angelino, No. 3,376,706; McEwen, No. 3,516,248; and Paxton, No. 3,512,357.

In addition, there is described in Chemical Abstracts, Volume 65, 1966, on page 11791, the use of fluorochemicals as working fluids for small Rankine cycle power units. 1

SUMMARY OF THE INVENTION The invention can be described asa working fluid primarily used in a Rankine cycle engine, which consists of hexafluorobenzene and perfluorotoluene.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a description of the prior art showing the operating characteristics of a Rankine cycle engine.

FIG. 2 is a eutectic graph of the temperature vs. physical characteristics of the two fluids.

DESCRIPTION OF THE PREFERRED EMBODIMENT Shown in FIG. 1 is a typical Rankine cycle engine. A

heat source is shown at 2 which vaporizes the working fluid for a vaporizer 4. This vapor travels in a direction I of arrow 6 to an expander and in the preferred embodiment is a turbine expander 8. This generates power which is transferred by shaft 10 to an alternator 12 to generate electrical power, or is transferred by shaft 10 to mechanical power, such as a transmission, or in the case of a steady-state power need, to a pump or another suitable mechanical mechanism.

Shown at 14 is a pump which, as indicated by arrow 16, delivers fluid to a regenerator 18. The regenerator 18, as shown by arrow 20, exits into the previously described vapor generator 4.

The regenerator 18, as shown by arrow 22, cycles the fluid to condenser 24 and as shown by arrow 26 into pump 14. v

This is a typical Rankine cycle power conversion system and it is considered as prior art. 4

The Rankine cycle power conversion system, as previously described, typically utilizes what is known as working fluid. In the past, this working fluid usually consists of water which is vaporized into steam at either a critical or a sub-critical phase. In other words, the water or other working fluid is vaporized by a source of heat and expanded into a turbine to produce work and the condensed fluid redelivered to the heat source and vaporized again.

PHYSICAL PROPERTIES Hexafluorobenzene 176F 480 psia Non-flammable Non-toxic Perfluorotoluene Boiling Point Freezing Point Empirical Formula Molecular Weight Critical Temperature Critical Pressure Flammability Toxicity 395 psia Non-flammable Non-toxic In FIG. 2 a eutectic liquid-solid-phase diagram for the aforementioned compounds is shown.

Thus it can be seen by the dotted line which is 25C the working fluid is in liquid phase and thus for most purposes is ideal for automotive propulsion use. Referring back to the physical properties, it can be seen that the freezing point is a compromise between the two compounds and that percentage of the components of that mixture can be selected depending upon the critical temperatureconditions, the critical pressure conditions, and other factors, to optimize the mixture ratio for any application.

The two constituents according to this invention can range in percentages of l to 99 percent of hexafluorobenzene and perfluorotoluene which is dependent upon the application in the Rankine cycle (preferably) application, and which may range from such aspects as automotive propulsion to electrical power conversion. In other words, the output of the Rankine cycle engine can be varied so as to meet the conditions of such applications as automotive propulsion and electrical power.

The advantage advanced by the mixture is their high efflciency, high temperature operation, inertness, noncorrosiveness, non-toxicity, and its safety.

What is claimed is:

1. A method for converting heat energy to another form of energy, which comprises:

vaporizing a fluid comprising a mixture of hexafluorobenzene and perfluorotoluene by passing said fluid in a heat exchange relationship with a heat source; and

utilizing the kinetic energy of the resulting vapors to perform work, wherein the amount of perfluorotoluene is sufficient to substantially reduce thefreezing point of the mixture, below the freezing point of hexafluorobenzene.

2. The method according to claim 1 in which said fluid is utilized in a Rankine cycle engine.

3. The method according to claim 2 in which a turbine expander is utilized to perform said work.

4. A method according to claim 3 in which mechanical energy is produced by said turbine expander.

5. Method according to claim 3 in which electrical energy is produced by said turbine expander.

3,753,345 3 4 6. A working fluid for power generation which comperfluorotoluene. prises: 7. A working fluid according to claim 5, having apa mixture of hexafluorobenzene and perfluorotolproximately equal amounts by weight of hexafluorouene, said mixture having a range of l to 99 perbenzene and perfluorotolune. cent of hexafluorobenzene and 99 to 1 percent of 5 

2. The method according to claim 1 in which said fluid is utilized in a Rankine cycle engine.
 3. The method according to claim 2 in which a turbine expander is utilized to perform said work.
 4. A method according to claim 3 in which mechanical energy is produced by said turbine expander.
 5. Method according to claim 3 in which electrical energy is produced by said turbine expander.
 6. A working fluid for power generation which comprises: a mixture of hexafluorobenzene and perfluorotoluene, said mixture having a range of 1 to 99 percent of hexafluorobenzene and 99 to 1 percent of perfluorotoluene.
 7. A working fluid according to claim 5, having approximately equal amounts by weight of hexafluorobenzene and perfluorotolune. 